1. Field of the Invention
This invention relates to an automatic transmission fluid cooling system for internal combustion engines used in trucks and other motor vehicles and, in particular, to a cooling system utilizing a concentric tube oil cooler in combination with a radiator.
2. Description of Related Art
Radiators for automobiles have evolved in recent years from soldered units made of copper and brass to mechanically assembled units having brazed aluminum cores and plastic tanks. Common to the two types of radiators has been an oil cooler installed in the outlet radiator tank for the purpose of cooling automatic transmission fluid by the engine coolant. Occasionally, automobile or light truck radiators are made with a transmission oil cooler in one radiator tank and an engine oil cooler of similar construction in the other tank. Such oil coolers have typically been either of the concentric tube type or of the stacked plate type. The stacked plate type oil cooler is typically higher cost, usually being made of stainless steel, and has higher performance than the concentric tube type oil cooler of similar size. The concentric tube type oil cooler typically consists of two concentric brass tubes welded together at their ends and has a lanced-offset inner fin between them for turbulation of the transmission fluid or oil.
While motor vehicle radiator design changes in recent years have resulted in lower cost and better-controlled product quality, e.g., by the use of brazed aluminum which allows the use of more highly automated and more consistent manufacturing processes, the oil cooler remains the single most expensive component of a radiator. There is a great need, both for original equipment and aftermarket radiators, to reduce the cost and improve the performance of this component, the design and installation of which has remained unchanged for many years.